Other than the lyric in my signature...
"If you are lonely when you're alone, you are in bad company." - Jean-Paul Sartre
And, because it always makes me laugh, an exchange from O Brother, Where Art Thou:
Ulysses Everett McGill: Pete, the personal rancor reflected in that remark I don't intend to dignify with comment. But I would like to address your general attitude of hopeless negativism. Consider the lilies of the xxxdamn field or... hell! Take at look at Delmar here as your paradigm of hope.
Delmar O'Donnell: Yeah, look at me.